1. Field of the Invention
The present invention relates to nuclear reactor installations in general, and more particularly to a novel method and means for remotely removing the guide balls from spent reactor control rods at such installations.
2. Background Art
Nuclear reactors commonly comprise a containment structure enclosing an array of nuclear fuel elements, the radioactive fuel material of which produces large amounts of heat while the fuel is consumed in nuclear chain reactions. A heat transfer medium is circulated around the fuel elements to recover the heat in a usable form. To control the chain reactions, control blades or "rods", are inserted into, or withdrawn from, the array, the rods containing materials such as cadmium or boron which readily absorb nuclear particles taking place in the chain reactions. The rate of the chain reactions decreases as the rods are inserted into, and increases as they are withdrawn from, the array.
As time passes, the control rods become radioactive and brittle, lose their effectiveness, and must be replaced. To accomplish this, the spent control rods, which may be 14-16 feet long, are withdrawn from the reactor by remote control and moved to an area called a spent fuel pool which comprises a large pool of cooled, distilled water, perhaps 40 feet deep, into which pool the rods are positioned underwater in fixtures on the bottom of the pool. The water prevents the escape of radiation, since it is poor absorber of radiation emitted by the radioactive rods.
As originally planned, nuclear reactor installations were to compact their high-level nuclear wastes and send them to centralized waste cites. However, political considerations dictated that such procedure be ended and, consequently, spent fuel pools are rapidly becoming filled. It is thus imperative that the volume of waste in such pools be reduced. One solution to the problem is to crush the control rods to a volume much less than that occupied by their gross dimensions. An impediment to simply removing and crushing the rods is that they include hard guide balls, usually manufactured of Stellite, which becomes extremely radioactive in the reactor. These guide balls constitute a personnel hazard and interfere with the crushing process. It would thus be desirable to be able to remove the guide balls from the spent control rods while the rods are still in the pool and to do so without the need for personnel to enter the pool or otherwise be in proximity to the control rods during the ball removal procedure.
Accordingly, it is a principal object of the present invention to provide a method and means for remote removal of the guide balls from spent nuclear reactor control rods while the rods remain positioned in a spent fuel pool.
It is another object of the present invention to accomplish such removal without the need for personnel to enter the pool.
Other objects of the present invention will in part be apparent and will in part appear hereinafter.